Chevrolet 2010 Tahoe Owner's Manual page 117

3. Push the latch plate into the buckle until it clicks.
Position the release button on the buckle so that
the safety belt could be quickly unbuckled if
necessary.
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4. For passenger seating positions with a lap
shoulder belt and a free falling latch plate, pull the
rest of the shoulder belt all the way out of the
retractor to set the lock. When installing a child
restraint using a lap shoulder belt and a cinching
latch plate, skip Step 4 and proceed to Step 5.